1. Field of the Invention
The present invention relates to a storage apparatus and control methods for detecting coil vibration generated in time of actuator drive and performing a control such that a head position error signal reduces based on the vibration detected signal, in particular, to a storage apparatus and a control method for detecting coil vibration in time of seek for positioning the head at a target track and in time of settling, and performing a control such that the head position error signal reduces based on the vibration detected signal.
2. Description of the Related Arts
Conventionally, a rotary actuator is driven by a voice coil motor in the magnetic disk device to move the head to an arbitrary target track of a magnetic disk medium to write data to the target track or to read the data already written on the track. The voice coil motor for driving the actuator fixes a yoke that uses a permanent magnet to a housing, supports a head at one end of an actuator supported at a shaft unit in a freely rotating manner with respect to the housing, and supports the coil of the voice coil motor at the other end by a coil support unit. When moving the head to the arbitrary target track on the magnetic disk medium, the current is first flowed to the coil to perform seek control. The seek control performs speed control by producing the profile of the target speed corresponding to the remaining number of tracks until the target track, and normally, performs acceleration control, constant speed control, and deceleration control.
FIGS. 1A and 1B show a head position error signal and an on-track signal when positioning on the target track by seek control. FIG. 1A shows a head position error signal 200, where switch is made from speed control to position control when reaching the target track after the seek operation 202. When the head reaches an on-track slice level range 206, which is a range defined from the center of the target track, an on-track signal 208 shown in FIG. 1B is raised to H level and becomes valid. The drawing to a track center 210 from when seek is completed until the on-track signal 208 rises is referred as settling 204. Writing of data and reading of recorded data are performed only when the on-track signal 208 is at H level.    [Patent document 1] Japanese Patent Application Laid-Open Publication No. 11-317033    [Patent document 2] Japanese Patent Application Laid-Open Publication No. 11-203808
However, in such conventional magnetic disk device, vibration may produce in the actuator during seeking due to mechanical accuracy such as parallelism of the coil supported by the actuator and the yoke fixed and arranged on the housing side. The vibration produced in the actuator during seek is referred to as seek residual vibration, where if the seek residual vibration is produced, the period of settling 204 of FIG. 1A from seek completion until when the head reaches the on-track slice level of the target track and the on-track signal rises becomes long. After the head position error signal 200 enters the on-track slice level range 206, an off track 212 of moving outside the on-track slice level due to influence of seek residual vibration may occur, when the off track 212 occurs, the on-track signal 208 lowers to L level and writing or reading cannot be performed, and must wait until the head again moves into the on-track slice level range 206. Therefore, seek residual vibration leads to lowering of device performance. Patent document 1 has been proposed to control the actuator for detecting the vibration produced in the actuator with a sensor and suppressing the vibration. Patent document 1 performs a control to detect and suppress the vibration of a so-called butterfly mode caused by in-plane swing deformation of the coil during the on-track in which the head is positioned on the target track by seek control, thereby stabilizing the on-track control. However, the control of detecting and suppressing the vibration of the actuator by the sensor of patent document 1 is performed during on-track, and does not address the seek residual vibration produced during seeking, and furthermore, the vibration during seeking is not taken into consideration for the various vibration modes that occur in the actuator, and thus the problem of the settling period becoming long due to the seek residual vibration thereby lowering the device performance is not solved. In patent document 2, the sensor is not used, and the state amount of the vibration mode and the rigid body mode of the actuator are estimated and controlled from a head reproduction signal and a movement command control amount of the actuator. However, similar to patent document 1, patent document 2 proposes a control in on-track, and the problem of the settling time becoming long due to seek residual vibration thereby lowering the device performance is not solved.